Took a sample of our water to an aquarium shop today & had it tested. Test for ph was 8.0 when ours still says 7.0 at home! His best guess was that there was something wrong with our test kit so I am going to look online for a new one (they are soooo expensive!). That means it must have been dodgy from the start & apart from a phosphate reading of 2.0 he was very happy with all the other results.
So relieved to find there isn't a problem after all!
Thanks to all for the support over the last few weeks - at least we now know that all was ok except for that one nitrite spike!
Yay! You can get digital pH meters that are really accurate, ebay would probably be the cheapest place. I still think you are worrying too much about the phosphate, did he try and sell you any phosphate-reducing stuff? Anyway, I'm glad you've got it all sorted, it would have started keeping me awake at night fairly soon